This invention relates to scaffolding equipment, and more particularly to upright poles for use with climbing pump jacks.
In working on exteriors of housing, and the like, it is customary to erect scaffolding to permit the workers access to the exterior surface and movement around the periphery of the house. The use of standard scaffolding is expensive and requires extensive amount of time to erect. Accordingly, it has become customary to utilize pump jacks which ride on upright poles and support a platform on which the workmen can stand.
The pump jacks are readily available, as for example, the pump jack sold by Hoitsma, Patterson, New Jersey. Such pump jacks contain shackles which clamp onto the upright pole and include a foot pump which is utilized for riding up of the pump jack on the upright. To descend, a release catch is provided which then permits the worker to crank down the pole by means of a hand crank. The pump jack integrally includes an extended arm on which can be placed a platform.
Typically, two pump jacks are utilized in conjunction with each other; each pump jack being installed on a respective upright pole. The upright poles are swung up and braced onto the exterior of the housing so as to be in a vertical position with the two uprights laterally spaced apart. Horizontal planks are then placed across the arms of the two pump jacks. The two pump jacks are then operated either by two separate workers substantially simultaneously, or by a single worker raising each side in sequence to thereby move the platform up and down the exterior of the housing.
The poles which are utilized for the uprights are formed by two 2 by 4s which are formed of wood. The two pieces of wood are fastened together by nails to form a single upright pole. The wood is generally carefully selected to be free of cross grain shakes, large loose or dead knots, or other defects which may impair strength and durability.
However, despite the care and selection of the wooden poles, there has been great difficulty in continued utilization of such poles and occasionally accidents have occurred by utilizing the well accepted wooden poles for such scaffolding.
One of the major problems of utilizing such wooden upright poles concerns the exterior surface of the poles. The pump jacks riding up and down the poles grip into the exterior surface of the poles. After continued use with the gripping and riding up and down of the poles, the poles become smooth and it becomes difficult to grip the poles. As a result, it is frequent that the pump jacks will no longer operate properly on the upright wooden poles and may actually slide down the poles. As a result, it is most important to continually change the poles every few months to be sure that sufficient gripping of the poles by the pump jack is obtained.
Additionally, despite the care in selecting and continuously replacing the poles, other deficiencies of the wooden poles continue to bring about accidents in utilizing such scaffolding equipment. For example, in swinging up the poles into a vertical position, the wooden material of the poles permit the poles to flex and oscillate. If the poles are swung up along the lateral surface of the poles, in many cases the pole will actually crack during the swing up. Such cracks may actually go unnoticed at the time of swingup and subsequently during use of the pump jack when the uprights are loaded, the crack may enlarge and the entire scaffold may collapse. In order to try and limit the possibility of the poles cracking, the poles are usually swung up along the butted surface of the 2 by 4s. However, even then the flexure of the wooden poles may still cause cracks to occur in the poles.
The use of the wooden poles also provides additional deficiencies as for example the shrinkage in size which occurs in wood after continuous use. Also, cracks can occur during the loading and unloading of the poles. The wooden material is also subject to damage by means of the weather conditions. Specifically, the wood may warp, it may bend during certain rain and moisture conditions, it may split due to expansion or contraction, and will provide for hidden latent defects which may go unnoted for some period of time until it causes an entire scaffold to collapse.
Because of the sway and flexure of the poles, it is generally necessary to provide additional bracing of the poles. Such bracing may include braces connected to the exterior surface of the house or the roof of the house, or may include interconnecting bracing between adjacent uprights. In either case, such extra bracing requires not only additional cost for the bracing, but requires time and effort to continuously connect and interconnect the bracing. This becomes especially a problem when the pump jacks must regularly ride up and down the poles and the bracing must be removed each time the pump jack approaches the brace.
Another problem with the use of the wooden poles concerns the splinting arrangement of lengths of poles. In order to provide a suitable length of approximately 30 or even 24 feet, the poles are interconnected in longitudinal sections. The poles are normally butt jointed with one section of 2 by 4 laterally spanning the butted ends of the adjacent 2 by 4s. When it is necessary to pick up an enlongated length of such pole, and if it is picked up from the center by means of a hoist, the weight from the two sides of the pole may cause the pole to crack.
Because of the aforementioned difficulties in utilizing the wooden poles, there have been many accidents, and even resulting deaths, due to the collapsing of some scaffold equipment. While attempts have been made to eliminate the wooden poles, thus far no acceptable substitute have been provided which would give adequate support for a platform and would permit secure riding of the pump jack up and down the poles.